From the LA Times four years ago:
The explosion destroyed the Times building, taking the lives of 20 employees, including the night city editor and the principal telegraph operator, and maiming dozens of others. Two other time bombs — intended to kill Gen. Harrison Gray Otis, the publisher of the newspaper, and Felix J. Zeehandelaar, the head of a Los Angeles business organization — were discovered later that morning hidden in the bushes next to their homes. Their mechanisms had jammed.This terror attack was part of a nationwide bombing rampage by the International Assn. of Bridge and Structural Iron Workers that damaged over 100 iron works.
Eventually, two brothers, J.B. McNamara, who planted the bombs, and J.J. McNamara, an official of the International Assn. of Bridge and Structural Iron Workers union who ordered the attacks, were arrested, convicted and imprisoned.
I bet you didn't learn about this sad day in American history in a high school or college class.